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FAQ: The Deadly Ebola Virus

Editor's note: This story was updated on March 13, 2015, with a U.S. health care worker flown to the NIH for treatment, and new case numbers.

April 4, 2014 -- Perhaps no virus strikes as much fear in people as Ebola, the cause of a deadly outbreak in West Africa.

The World Health Organization (WHO) reports more than 24,500 confirmed or suspected cases of Ebola, mostly in the countries of Guinea, Liberia, and Sierra Leone, as of March 10. Nearly 10,100 people have died in the largest Ebola outbreak ever recorded.

An infected U.S. health care worker arrived March 13 at the National Institutes of Health Clinical Center in Bethesda, MD, for treatment, the NIH said in a statement. The person, who was not identified, caught the virus while working as a volunteer at an Ebola treatment center in Sierra Leone, the NIH said.

No further information was released about the health care worker, who is the second American to be treated at the NIH facility. The first was Nina Pham, 26, a Dallas nurse who caught Ebola after treating Thomas Eric Duncan, a Liberian man who later died. Pham recovered from the virus.

She was one of two nurses at Texas Health Presbyterian Hospital who caught Ebola after treating Duncan. The second, Amber Vinson, 29, also recovered after being treated at Atlanta’s Emory University Hospital.

Duncan arrived in the U.S. on Sept. 20, 2014, to visit relatives. Ten days later, he became the first person to be diagnosed with Ebola in the U.S. He died Oct. 8, 2014.

In November 2014, a surgeon from Sierra Leone who lives in the United States died after being flown to the Nebraska Medical Center for treatment. Martin Salia, who was reportedly working at a hospital in the Sierra Leone capital of Freetown, arrived in the U.S. Nov. 15 and was taken to the medical center.